The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.
The ability to quickly generate indicators that uniquely identify certain characteristics of a digital image is important in image processing and image classification. The indicators may be used to group the images based on similarities between the images, and to identify groups containing similar images. The groupings of the images may be captured using an index that maps the indicators onto the corresponding images. However, generating such an index for a vast amount of images in a relatively short period of time is usually unachievable using conventional approaches.
Indexes generated for digital images may be used in a variety of applications. For example, an index may be used to determine whether a newly received image is similar to any of the already classified images. Upon receiving a new image, an indicator may be generated for the image and the generated indicator may be compared with the indicators that have been already generated for other images. The comparison may allow determining whether the received image is in some sense similar to the other images.
However, making such a determination using conventional approaches is often not only inefficient, but also unreliable. For example, the indicators generated using the conventional approaches are rarely invariant to the image rotation or resizing. Thus, such indicators are seldom helpful in determining whether a received image is indeed similar to any of the already classified images. For example, it may be difficult to determine whether an image created by a competitor infringes on a trademark registered to another party if the competitor's design is merely a rotated copy of the registered mark, or it may be difficult to locate similar digital images in a database that contains a large number of digital images that are slightly different yet generally similar.